Adherence and discontinuation of prescription cannabidiol for the management of seizure disorders at an integrated care center.

OBJECTIVE: Evaluate adherence, discontinuation rates, and reasons for non-adherence and discontinuation of prescription CBD during the 12-months post-initiation period at an integrated care center. METHODS: This was a prospective study of patients prescribed CBD by a neurology clinic provider with initial prescription fulfillment through the center's specialty pharmacy from January 2019 through April 2020. Baseline demographics and reasons for non-adherence and/or discontinuation were collected from the electronic health record and pharmacy claims history was used to calculate adherence using proportion of days covered (PDC). Patients were included in the PDC analysis if they had at least 3 fills during the study period. Non-adherence was defined as a PDC < 0.8. Descriptive statistics were used to summarize data with categorical variables represented as frequencies and percentages and continuous variables as medians and interquartile ranges (IQRs). RESULTS: We included 136 patients with a median age of 14 years (IQR 9 - 21). Most patients were white (n = 115, 85%), with a diagnosis of intractable epilepsy (n = 100, 74%). Among the 128 patients with 3 or more fills, the median PDC was 0.99 (IQR 0.95 - 1.00) with non-adherence seen in 6% (n = 8) of patients. The most common reason for non-adherence was side effects (n = 2, 25%). Prescription CBD was discontinued by 23% (n = 31) of patients with a median time to discontinuation of 117 days (IQR 68 - 216). The most common reason for discontinuation was major side effects (n = 12, 39%). The most common side effects leading to discontinuation were agitation/irritability (n = 4), mood changes (n = 4), aggressive behavior (n = 3), and increased seizure frequency (n = 3). CONCLUSION: Adherence to prescription CBD at an integrated care center was high with approximately 94% of patients considered adherent. Providers and pharmacists may improve adherence and discontinuation rates by educating patients on the timeline of response, potential side effects, and potential for dose adjustments.

Mechanistic Investigation of the Time-Dependent Aldehyde Oxidase Inhibitor Hydralazine.

The anti-hypertensive agent hydralazine is a time-dependent inhibitor of the cytosolic drug-metabolizing enzyme aldehyde oxidase (AO). Glutathione (GSH) was found to suppress the inhibition of AO by hydralazine in multiple enzyme sources (human liver and kidney cytosol, human liver S9, rat liver S9, and recombinant human AO) and with different AO substrates (zoniporide, O6 -benzylguanine, and dantrolene). Hydralazine-induced AO inactivation was unaffected when GSH was added to the incubation mixture after pre-incubation of hydralazine with AO (rather than during the pre-incubation), suggesting that GSH traps a hydralazine reactive intermediate prior to enzyme inactivation. Consistent with previous reports of 1-phthalazylmercapturic acid formation when hydralazine was incubated with N-acetylcysteine, we detected a metabolite producing an MS/MS spectrum consistent with a 1-phthalazyl-GSH conjugate. O6 -Benzylguanine, an AO substrate, did not protect against hydralazine-induced AO inactivation, implying that hydralazine does not compete with O6 -benzylguanine for binding to the AO active site. Catalase also failed to protect AO from hydralazine-induced inactivation, suggesting that hydrogen peroxide is not involved. However, an allosteric AO inhibitor (thioridazine) offered some protection, indicating a catalytic role for AO in the bioactivation of hydralazine. AO inhibition by phthalazine (a substrate and inhibitor of AO and a metabolite of hydralazine) was unaffected by the presence of GSH. GSH also prevented hydralazine from inhibiting the nitro-reduction of dantrolene by AO. Furthermore, the GSH-hydralazine combination stimulated dantrolene reduction. Phthalazine inhibited only oxidation reactions, not reduction of dantrolene. Together, these results support the hypothesis that hydralazine is converted to a reactive intermediate that inactivates AO. SIGNIFICANCE STATEMENT: These studies suggest that a reactive intermediate of hydralazine plays a primary role in the mechanism of aldehyde oxidase (AO) inactivation. Inactivation was attenuated by glutathione and unaffected by catalase. Phthalazine (hydralazine metabolite) inhibited AO regardless of the presence of glutathione; however, phthalazine inhibited only oxidation reactions, while hydralazine inhibited both oxidation and reduction reactions. This report advances our mechanistic understanding of hydralazine as an AO inhibitor and provides information to facilitate appropriate use of hydralazine when probing AO metabolism.